1. Field of Invention
This invention relates to a method and an apparatus for continuously and uniformly supplying highly viscous and elastic dough through a narrow space at the bottom of a hopper during a bread-making process.
2. Prior Art
Dough is a fluid material with a high viscosity and elasticity due to its gel structure. This high viscosity causes a dough mass to resist stretching into a sheet by uniform and continuous feeding from a hopper through a narrow space between opposing rotating rollers.
A conventional apparatus which may be used to form a dough sheet using opposing horizontal rollers is disclosed in Japanese Patent Publication Nos. 5-3253 and 6-37. Dough is continuously fed between the rollers, which press the dough to form a sheet having a constant thickness and width. However, this conventional apparatus cannot make a thin sheet of dough. Also, this conventional apparatus does not completely prevent the loss of elasticity of the dough.
FIG. 1 illustrates a conventional apparatus. This conventional apparatus includes a hopper 1 which stores a dough mass 3. Rollers 2 and 2' are positioned below a bottom opening of the hopper. The rollers 2 and 2' are fixedly positioned opposite to each other and such that a fixed gap c is formed where the rollers 2 and 2' face each other.
The conventional apparatus cannot be used to form a sheet of high viscosity dough for the following reasons. A study revealed that, as illustrated in FIG. 1, when the rollers 2 and 2' are rotated in the direction of arrows a, the dough 3 in the hopper 1 flows in the directions of arrows b1 and b2 (that is, upward away from the gap c). This phenomenon is caused by stresses in the dough 3 which are located at and above the gap c. As the rollers 2 and 2' rotate in the directions of arrows a to push the dough 3 in opposite directions toward the gap c, the two flows collide with each other, and then flow together in the directions of arrows b1 and b2 (that is, away from the gap c between the rollers 2 and 2'). The reason why the dough 3 flows away from the gap c is that the amount of stress in the dough 3 adjacent the gap c is higher than that at an upper portion of the dough 3. Thus, it is difficult for the dough to flow toward the gap c between the rollers 2 and 2'.
In an alternative conventional method, in order to uniformly and continuously produce a sheet of dough, dough portions are separated from a dough mass prior to pressing between a pair of rollers. In particular, a piston and a cylinder are provided at the bottom of the hopper. A predetermined amount of dough mass is drawn by the piston into the cylinder, then the dough portion is separated (cut) from the remainder of the dough mass, and, finally, the separated dough portion is extruded by the piston from the cylinder such that it passes between a pair of opposing rollers. These steps are repeated such that a continuous dough sheet is produced by the rollers.
Several problems are associated with the above-mentioned conventional method. First, the piston and cylinder mechanism, along with the associated separating process, is complex. Further, the process steps repeatedly exert a shearing stress on the dough, thereby causing the dough to lose elasticity. Thus, a resting step is needed after the sheet is formed, and a chemical additive such as potassium bromide is typically used to allow the elasticity to recover before bread is made from the dough sheet.